One of the most significant disadvantages when examining case studies is possible bias in data collection and interpretation. In Dr. Crawford's book, Introduction to Research: Less Fright, More Insight, Crawford explains biased data collection that disqualifies the results of different case studies. Disqualifying factors such as biased selection and biased testing pose a major problem for researchers because if the data is collected in a biased manner, the entire case study may be considered flawed. Therefore, it is important for the researcher to embark on their experiment with a single-blind study or a double-blind study in order to reduce potential threats associated with data collection and interpretation.